Hidden Charges on my Credit Card

On my statement I saw 5 charges on the 4th of Dec 2017 to the value of R 8.50 each x 5 = R 42.50. Upon inquiry the charges related to insufficient funds in my credit card. I had this issue in the past where I maybe need R 1000.00 in my card but the transaction will still clear, but in this case I needed an extra R 1300.00 for a R 30 000.00 transaction which for me is unnecessary to decline because of the size of the transaction. The merchant then tried to pass the sale 5 times but with no luck.

I've went on Nedbank's website to see if these type of fees are disclosed but I could not find any.. I phoned Nedbank and it was told that it was implemented in Sept 2017 but without any communication to the clients.

I would love to hear some feedback on how this issue woudl be cleared as I think when it comes to costs Nedbank should be clear or at least warn customers.

Thanks